Light responsive system



May 25, 1954 G. W. ONKSEN, JR., ETAL LIGHT RESPONSIVE SYSTEM 2 Sheets-Sheet 1 Filed July 10, 1948 Jnventors I I ,v .4 ttomegs y 25, 1954 s. w. ONKSEN, JR., ETAL 2,679,616

LIGHT RESPONSIVE SYSTEM 2 Sheets-Sheet 2 Filed July 10, 1948 620g? WQYiiaI c /E Kiel/er Patented May 25, 1954 UNITED" STATES PATENT OFFICE George W. Onksen, Jr., and Charles W. Miller,

Anderson, Ind., assignors to General Motors; Corporation, Detroit, Mich., a corporation of.

Delaware Application" July10, 1948, Serial No. 37,984

18 Claims. 1,

The present invention relates to illumination systems and more particularly to light-sensitive electrical circuits adapted to control vehicle illumination systems in responseto the'intensity of illumination of a similar approaching system.

The illumination systems of automotive vehicles are generally provided with dual filament headlamps with each filament in separately energizable electrical circuits controlled for alternate energization by the operator. The fila-' ments are positionedwith respect to the headlamp reflector toproject a high and low beam of light'declining to the longitudinal axis 'of the vehicle at different-angles so that illumination patterns are cast at difierent' distances in its path ahead. The high beam is generally preferred for night driving on rural highways which are not illuminated'from'other' sources, whereas the low beam is generally used for city driving conditions where additional illumination is'provided.

To eliminate the hazards of 'passing'due to the glare and dazzling eifect oi'the high beam, 'the' operator is required to manually'operate a switch which selectively energizes the low beam circuit. This operation may distract the ope'rators'attention from the path ahead and when the operator fails to depress the beam, extremely hazard= ous conditions prevail for the p'assingof oncom ing operators.

It is therefore an object'of the present in ven tion to minimize the driving'hazards prevalent under conditions of night driving'by providinga light-sensitive electrical circuit for auto'm'a'tically controlling the illumination system of vehicles in response to the intensity of illumination of a similar approaching system.

This and other objects areobtainedin accordance with the present invention by providing a selective light-sensitive electrical circuit for controlling vehicle headlighting systems which is responsive to a predetermined light intensity to dim the system yet may be subjected to a wide variation of light intensity without alfecting a de-energization of the dim circuit once-it has been energized. A headlight'system embodying the present invention comprises the conventional dual filament headlamps with independent electrical circuits for energizing one or the other, a light-sensitive electrical circuit including a photoelectric cell, a first and second stage of amplification, a relay for selectively energizing the independent filament circuits and a common source of electrical energy. The responsiveness to a predetermined light intensity while remaining unafiected'by wide variations of light intensities once the system has been dimmed is obtained by including'in the second stage of amplification, two amplifier tubes of differing characteristicselectrically connected in parallel.

Further objects and'advantages of our invention will become apparent" as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed toand forming part of this'specification.

For better understanding of our invention reference may be had to the accompanying drawings in which Figure 1 a schematic diagram of the circuit'utilizing the present invention for controlling a vehicle headlighting system; Figure 2 is a schematic diagram illustrating one form of modification and Figure-3 is a schematic diagram illustrating still another modification.

Referring now to. Figure 1 of the drawings, there is illustrated a vehicleheadlighting system embodying the present invention in which 'a pair of conventional headlamps, not shown, including high and low beam filaments 2 and 4 respectively, form part of electrical circuits energizable to provide either a manual or automatic control of the system. 7 I

In the system, a conventional automotive vehicle storage battery 6 of the fi-volt type is provided as a sourceof electrical power. In this connection it will be understood that the battery 6 is a source ofpower for the ignition system of the vehicle as well as the lighting system. Thenegative terminal of battery 6 is connected to through conductor 8 to the movable arm H] of a single pole, single throw master switch l2. The stationary contact [4 of switch 12 is connected through conductor 16, current limiting fuse l8 and conductor 20 to a terminal junction 22. A branch conductor 24 connects terminal2'2 with the movable arm 26 of a single pole, double throw electromagnetic relay switch 28 provided with oppositely disposed stationary contact terminals 30 and 32. The movable arm 26 of switch 28 is normally held in yielding engagement with Sta-- tionary contact terminal '32 which in turn is connected through conductor 34 to the low beam filaments 4 of the headlamps. The other sides of the headlamp filaments 4 are grounded through a conductor 36'; The circuit comprising contact 32, conductor 34, filaments 4 and conductor 36 form one branch of the headlamp circuit. The other branch comprises-a conductor 38 which connects the high beam filaments 2 of the headlamps to contact 30 of the switch 28 and conductor 40 which connects the other sides of the filaments 2 to ground.

To provide for the independent manual energization and deenergization of the headlamp circuits, the solenoid coil 42 of switch 28 forms part of a circuit which includes in series relationship a single pole, double throw, selector switch 44 and a single pole, double throw foot selector switch 46. Terminal 22 is connected to the movable arm 48 of switch 44 through conductor 50. The movable arm 48 is shown in a position to bridge two stationary contacts 52 and 54, both of which are connected in circuits to the automatic control and indicating means and will be described in detail hereinafter. An oppositely disposed contact 56 of switch 44 is connected through conductor 58, terminal 50, conductor 62, terminal 04 and conductor 66 to a stationary contact 68 of the foot selector switch 46. The movable arm 10 of switch 46 is adapted to engage contact 68 and complete a circuit through conductor 12, solenoid coil 42 of switch 28 and conductor 14 to ground.

For automatic control of the headlamp filaments a circuit is provided from the source 6 to the solenoid coil 42 which includes a light-responsive, single pole, single throw electromagnetic relay switch 16 capable of energization and deenergization at substantially diiferent current values. In this circuit the stationary contact 52 of selector switch 44 is connected by a conductor 18 to a terminal junction 80 which in turn is connected to the movable arm 82 of relay switch 16 through conductor 84, terminal junction 86 and conductor 88. The movable arm 82 cooperates with stationary contact 90 of relay switch 16 and is normally in yielding open circuit relationship. Contact 90 is connected through conductor 92, terminal junction 94 and conductor 96 to the remaining oppositely disposed stationary contact 98 of foot selector switch 48.

To reduce the destructive effect of arcing between the movable arm 82 and the stationary contact 90 of relay switch 19, a shunt circuit including a 100 ohm resistor I and a .l mfd. capacitor I02 is connected in series between the terminals 86 and 94.

In the headlighting system of the present in vention the voltages suitable to the most efficient operation of the light responsive apparatus are provided by a conversion device I04 for changing the low voltage direct current of the vehicle electrical system to a high voltage direct current suitable for the operation of the electronic elements in the circuit. Conversion devices such as the device employed in the system of the present invention are well-known and are employed extensively to provide suitable voltages for the operation of vehicle radios. In this connection the positive input terminal I06 of the converter is connected through conductor I08, terminal junction I I0 and conductor H2 to the terminal 8|!v The negative terminal H4 is connected to ground by conductor I I I. The high voltage output terminal III; is connected by a conductor II8, terminal junction I20, conductor I22, terminal junction I24 and conductor I26 to the solenoid coil I28 of the light responsive relay switch 16. The negative output terminal of the converter is connected within the converter to ground through terminal I I4. The light responsive relay 16 has the other end of its solenoid coil I28 connected through conductor I90, terminal junction I32, conductor I34, terminal junction I36, a 25,000 ohm resistor I38 and conductor I40 to the stationary contact I42 of a single pole, single throw, manual switch I44. The movable arm I45 of switch I44 is in yielding open circuit relation with contact I42 and is connected to ground by conductor I46. A shunt circuit is provided for the solenoid coil I28 of relay switch 16 which includes an 8 mid. capacitor I43 connected between the ends of the solenoid coil.

'To provide the difierent voltages necessary to the operation of the various electronic elements in the light responsive apparatus a voltage divider network I41 comprising 4 sections of seriesconnected resistances I48, I50, I52 and I54 of 5800 ohms, 3900 ohms, 800 ohms and 15,000 ohms respectively, is connected between the high voltage terminal' I24 and ground. The respective resistances are connected together in the order enumerated by terminals I58, I58 and I90.

A filter I82 of 16 mfd. capacitance is connected across the output terminals H0 and II by means of conductor II8, terminal I20, conductor I68 and conductors I10 and III, to minimize the A. C. ripple voltage that is present in the output circuit of the converter I04.

As the voltage at the output terminals of the converter varies between about 260 and 420 volts due to the variation of the vehicle system voltage between about 5.5 and 7 volts, voltage regulator means I64 and I68 are connected in parallel with sections of the voltage divider network I41 to obtain stable voltage levels of 150 and 75 volts respectively. ihe voltage :regulator means I04 and-I comprise a VB 150 glow discharge tube which is connected by conductors I12 and I14 between terminal I58 and ground, and a VB. glow discharge tube which is connected by conductors I16 and I18 between terminal I and ground.

The electronic elements that comprise the light responsive apparatus and provide for the energization and deenergization of relay switch 16 include a photocell I19 which controls a power amplifying tube I90 hereinafter referred to as a first stage or primary amplifier and a pair of power amplifying tubes I93 and 206 which are controlled by the output of the primary amplifier and have their plates connected in parallel to the solenoid coil I28 of the relay switch 18. The pair of amplifying tubes I98 and 208 will be referred to hereinafter as the second stage or secondary amplifier. The photocell I19 is connected to the voltage divider I41 by a conductor I80 which connects its anode terminal to terminal I58 at the junction of the voltage divider resistance sections I50 and I52. By connecting the photocell anode to the voltage divider at this point, a voltage of about to volts is provided for the operation of the cell at the most efiicient portion of its response curve. The cathode of the photocell is connected by conductor I8I to a terminal junction I82 which in turn is connected through a 500 megohm resistor I84 to ground and to the positive terminal of a one and one-fourth volt biasing battery I88 which has its negative terminal connected by a conductor I88 to the control grid of the multiple grid power amplifying tube I90 comprising the first stage or primary amplifier. The output or plate of tube I90 is connected by conductor I92, terminal junction I94 and conductor I96 to the control grid of the multiple grid power amplifying tube I98 comprising part of the second stage or secondary amplifier and through terminal I94, resistor I95, terminal junction I91,

genera conductor 200*} resistor 202 and conductor 204 to th'e control grid of th'e'multipleg-rid power arn-plifying tube 296- comprising the other part o'f the second sta'ge or secondary amplifier. The resistors I95 and 222 have respectiveresistance values-T2 and 100 megohms. The plate of tube I90 is also connected by terminal I9! to terminal IB'II of the voltage divider through an 8 megohm resistor'208', conductor 21!]; terminal junction 212 and conductor 2M".- At 70,000 ohm potentioirieter 2| 3-is connected between terminal M2 and ground'and carries a sliding contact 2H5 which is connected by a conductor 2H3 to the screen grid of first stage amplifying tube I953:

2I8; an automatic regulating ballast resistance 220", a junction terminal 222 and a 25 ohm resistor 224. Current is also supplied from the battery to the filament of tube I98 through the choke coil 2I8 and ballast resistor 229 by con-' necting terminal 222 to the filament through conductor 226. The other sides of the filaments of tube I9ll'and I98 are connected to ground. To obtain a stable voltage input of 150 volts to the screen grids oftubes I 98 and 222 of the secondary amplifier, they areconnected in series by conductors 228 and 230' to the 15o'volt terminal I BG to'the voltage divider I41. Voltages for the cathodes of tubes'ldii and 286 are supplied from the voltage divider I47, the cathode and suppressor grid oftube I98 being connected by conductor 232 to terminal 2 l 2 and the cathode and suppressor grid of tube 206 being connected by conductor 234 to the sliding contact 232 on the potentiometer section I54. The cathode of tube" 206 is heated by an independent filament a which has one side connected by conductor 235 to the 6-volt battery source at the junction'of conductor 88 and movable'arm 82 of switch I6 and the other side connected to ground. The

plates of the tubes I98 and 206 are connected'ih parallel to the solenoid coil I28 of relay switch I6, the plate of tube 286 being connected to ter minal I32 through a 30,000" ohm resistor I33'and the'plate of tube I98 being connected to terminal I36 by conductor 238. V

Indicating means for the light responsive and manual control circuits are included in thes witching circuit. These means comprise indicator lamps 246' and 242.

ment connected to the contact 54"of;switch 44 by conductor 246, junction terminal 248 and conductor' 250. The filament of lamp 242 has one side connected to ground and the other side connected through a conductor 252 to the stationary contact 254 of an electromagnetic relay switch 255. The movable arm 255 of the relay switch 2561s in yielding closed circuit relationship" end of the coil through a conductor 265 to ter-' minal 64' and the other end of coil to terminal In thecircuit'modification of the light responsive apparatusillustrated in Figure 2, the at rangem'ent of the circuit and electronic ele ments is'substantiallyth'e'same as that of Figure Lamp 242 has one side of its' filament connected to terminal by' conductor 244 and the other side of the fila- 1 except that a'duoi diode tube 25'6-"is"corin'ected between the multiple grid tube I of the primary" amplifier and the multiple gridtube'206' of the"- secondary amplifier.

In this circuit the plate of the primary am-' plifier'tube I9!) is connected to terminal l94-by conductor I92 with branch circuits connecting terminal I94 with the controlgrid of tubel98;

one of the cathodes of tube 256' and the '75 volt The circuit connecting the-grid of tube I98 and the plate of tube ISO is the-same as -h'ereinabove described in terminal of the voltage divider I47.

connection with the circuit of Figure 1. The

circuit to the I5 volt terminal of the voltage"- divider includes a 'lomegohm resistor 260 con-*- nected betweenter'minals I94 and 212 by con? A conductor 25%; connects doctors 253 and terminal I94 with the cathode of tube 256. The voltage of the control grid of tube-206 iscontrolled bythe output plates of tube 256. These" plates are connectedin parallel circuits'toa terminal junction 255 which is connected to the control'grid of tube 205 by conductor 261. One plate of the diode is connected to terminal2S5" to terminal 265 by conductor 264. The heater filaments of tube 256' are connected in series between ground and the conductor'235-by conductor 2'. The remaining cathode of tube 256" is connected through a- 2 megohm resistor 213 to the cathode of tube 206.

In the circuit modification of the light re--' sponsive apparatus illustrated in Figure 3'there is included a pairof multiple grid tubes 27B and 212 comprising a first stage or primary amplifier which have their-outputs controlled by'the photo-f cell and which in turn control the outputs of anotherpairof multiple grid tubes 2l4and 276 comprising a second stage or secondary amplifier.

In this circuit arrangement the control gridof tube 212 is connected to the cathode of the photocell I19 through conductor 218, terminal junction 28!! and a 1 ,4 volt biasing battery 282 which is arranged with its negative terminal connected to the control grid and the" positive terminal connected to the terminal 289.

circuit'through terminal IIO choke coil 2I8 anclballast resistor 22!) and the branch circuits comprising the'con'ductors 294 and-296. The filaments oftubes 2'50 and 212 are connected in series circuit relationship between conductor 294 and ground by conductors 298 and 382 while the filament of tube 276 has one'side connected to ground by conductor 3il2and the other side connected to the conductor 2%. Voltage is sup plied to the screen grid of tube 212 by a circuit which connects one end of a 70,000 ohm potentiometer 324 to the 75 volt terminal I 60 of the voltage divider MI and the other end of the resistor to ground. Resistor 304 is connected to terminal I60 by a circuitwhich includes'con ductor'Z I4; junction terminal 388, conductor 310,"

The other plate-of tube 256' is connected A 100 megohm resistor 224 inseries with a 500 megohm; resistor 286 are connected between terminal 23?)- The plates of tubes 21!) an a aew junction terminal 3I2, conductor 3I4, junction terminal 3I6 and conductor 9H3. A slidable contact 329 associated with the potentiometer 394 is connected by a conductor 322 to the screen grid of tube 212. Voltage is supplied to the screen grid of tube 219 by connecting the grid through conductor 324 to a slidable contact 239 which is associated with the potentiometer section I54 of the voltage divider I41. The cathodes and suppressor grids of tubes 219 and 219 are connected respectively to terminals 398 and 3I6 by conductors 328 and 339; the suppressor grid of tube 234 being connected to the cathode externally by conductor 321. A 250,990 ohm resistor 332 and a 500,000 ohm resistor 334 are connected respectively between the plate of tube 219 and terminal 3I2-and the plate of tube 212 and-terminal SIB. Current is supplied to the filament of tube 214 by conductor 235 which is connected between the movable arm 82 of relay switch I5 and one side of the filament.

The other side of the filament of tube 279 is connected to ground by conductor 338. The plates of tubes 214 and 216 are connected respectively to terminals I32 and I39 in the coil circuit of relay switch I6 through a 100,090 ohm resistor 349 and conductor 342.

For the hereinabove described light responsive circuits to operate in response to predetermined light intensities to control the energization and deenergization of the headlamp filaments 2 and 4 through relay switch I9 it is first desirable to adjust the circuit to respond with predetermined current flow at the plate output of the tubes of the secondary amplifier. In this connection, switches I2 and 44 are closed to energize the current converter I94. The electronic elements which are connected to the high potential side of the converter are allowed to heat for a period of time so that they will operate efficiently. The sliding contacts of the three circuits are then adjusted to provide current flow through coil I29 which will vary in accordance with the intensity of light of an approaching vehicle headlight system to cause deenergization of the coil when the approaching vehicle is at a predetermined distance ahead and energization of the coil when the approaching vehicle passes by.

To provide for the automatic control of the headlighting system, switch I9 is closed to energize the low beam filaments 4 through current flow from the battery 6 through conductors 9, I6, I8, 29 and 24, movable arm 28 and conductor 34. The movable arm 48 of switch 14 is then closed on contact 52 to energize the converter I94 through the circuit including conductors '58, H2 and I98.

Referring now to the circuit diagram of Figure 1 with the electronic elements sufliciently heated and no light on the photocell I19, sufiicient current flows in the circuit from terminal I I9 of the converter through conductors H8, I22, I25, coil I28, conductors I39 and I34 to the plates of tubes I98 and 296 to cause energization of the relay coil I28 and movement of arm 82 of relay switch I9 into engagement with contact 99. With the movable arm I9 of the foot switch 49 engaging contact 99 a circuit is completed to coil 42 from the battery through conductors 8, I9, 29, I8, 89, 88, 92, 96 and I2. With coil 4?. energized the movable arm 26 of relay switch 28 moves into engagement with contact 39 causing energization of the high beam filaments 2.

With the approach of a similar lighting system, light of gradually increasing intensity falls on the photocell I'I9 causing anincreasing current flow ductors 2I4, 2I9, resistors 298 and I and conductor I92 to the plate of tube I99 increases and a voltage drop occurs at terminals I9! and I94 due to the IR, drop across resistors I95 and 298. These voltage changes are carried to the control grids of tubes 296 and I98 respectively through circuits including conductor 299, resistor 282 and conductor 294 and conductor I98 respectively. This causes a change of grid bias on the control tubes I98 and 299 causing both tubes to become sequentially non-conducting; tube I98 being the first to cut off but relay I28 will not drop out until tube 299 is cut down in conductance to a low value after tube I98 is nonconducting. With very little or no current flowing to the plates of tubes 299 and I98 the coil i28 of relay I9 is deenergized moving arm 82 out of engagement with contact 99 and the circuit through coil 42 of relay 28 is broken causing the movable arm 29 to move into engagement with contact 32 for the energization of low beam filaments 4 and the deenergization of high beam filaments If the source of illumination to which th photocell is exposed then begins to decrease in intensity, a current of decreasing value flows from the terminal I58 of the voltage divider through the circuit including the photocell to ground as hereinabove mentioned. Accordingly, the voltage at terminal I82 decreases until the voltage of the biasing battery is imposed on the control grid of tube I99. The flow of current through tube I99 decreases and consequently the voltages at terminals I91 and I94 increase altering the grid bias in tubes 296 and I98. As these biasing voltages change the flow of current in tube 295 gradually increases to normal value, and tube I98 begins to approach the conducting point. However, while tube I98 remains non-conductive there is insufficient current flow in the coil circuit of relay I9 to cause it to move the arm 82 into engagement with contact 99. When it does become conductive sufficient current fiows in the relay circuit to cause relay IE to move the arm 82 into engagement with contact 99 and filaments 2 and 4 of the headlamp circuit re spectively are energized and deenergized. There is thus a definite difference in the illumination level at relay drop-out to that at relay return. With this arrangement it will be obvious that substantial changes in intensity of illumination are required before the relay 29 will be energized or deenergized from its existing state thereby preventing flickering or repeated alternate energization of the filaments due to extraneous lighting conditions.

If the operator of the vehicle should desire to reenergize the high beam elements 2 while the low beam elements are energized and under the control of the light-responsive apparatus, the independent resetting manual foot switch its is provided to close a circuit through the coil I29 of relay "I9 from the terminal H9 of the con verter I94 to ground. This circuit comprises conductorslla, 1 22, l26,re1ay-coil I2B,conductors 1,30,.134, resistor;|38, conductor l llbswitch 14-6 ,and conductor I46.

Manual controlof-the filaments zandxl is obtained in the same manner as in the conventional headlight system. In this connection the -movable arm 38 of selector switchAJl .is moved into engagement with contact 56 thereby completing a circuit from battery 6 through conductors-8, I6, 20, 50, 58, 62 and as to the stationary contactfie of the foot switch 45. .When the movable arm 1c moves into engagement with. contact 68, the circuit is completed from the battery 6 tothe coil of relay 28 through theswitch .46 and conductor 12. Movable arm '26 of relay switch 23'moves into engagement with contact 30 and the high beam filaments 2 are energized. Manually. breaking the circuit at switch as causes a deenergization of relay coil 42 and an energization of. the circuit to the low beam filaments c.

Lamps 240 and 242 indicate the controlling condition of the light responsive apparatus andthe respective energization of the headlamp filaments.

With'the movable arm 48 of switch 44 in engagement withcontacts 52 and 54 forenergization of the light responsive apparatus as hereinabove described, a circuit is completed from terminal 248 through conductor 24,5, lamp 240 and conductor 244 to terminal 60. An additional circuitis completed from terminal 248 through .conductor 261,.coil 263. ofrelay switch 2.56 and conductor 265 toterminal 64. This circuit also includes a branch circuit from conductor 26! to the movable arm 255 through conductor 251.

Withthe coil of relay switch 256 deenergized, this circuitis completedthrough contact 254, conductor 252 and lamp 242 to ground. When thearm 1 of switch 46 isin engagement with contact 98 for control of the filaments 2 and 4 by the light responsive apparatus, lamp 242 is energized, indicating that the lightresponsive apparatus is controlling. When the movable arm of switch 46 movesinto engagement with contact 68, coil 26.3 of relay 256 is energized moving arm 255 out of engagement with contact 254 whereby the lamp 242 is deenergized. At the same time, lamp 240' becomes energized. With switch arm .48

movedout of engagement with contact 54.both indicating lamps become deenergized. Withsuch an arrangement of indicating lamps there is visual means for indicating whichof the headlamp filaments is energized when they are controlled manually and whether the filamentsare under the control of the light responsive apparatus.

The operation of the light responsive circuit of Figure 2 is substantially the same as that. of Figure 1. In this circuit, the intensity of light on the photocell determines the current fiow in tube I90 and through resistor 260 which in turn controls the current flow in tubes I98 and 206 by changing the voltage on the control grids .of these tubes. With no light on the photocell,

-In the light responsivecircuit of Figure 3 the operation is substantially the .sameas that of light responsive circuits of Figures 1 and 2 except thatthe flowof cur-rent through tubes 214 and. 21.6 is d irectly and separately. controlled by .tubes .210 and .212 respectively of the primary amplifier. These tubes ofthe primary amplifier .are in turncontrolled by the photocell. As in the light responsive circuits of Figures 1 and2 ,when the photocell isnot exposed to light tubes a 214 and 216 both conduct current of substantially high valueto energize ,relaycoil I28. As the intensity of light on the photocell increases the photocell conducts increasingly more current in the circuitfrom the voltage divider to ground through the photocell, conductor, 218 and resistors 2B4 and 2 86. ,Withincreasing current in this ,circuitvoltag changes occur across resistors 28 4 and 286 to cause the voltage bias on the control grids oftubes 210and 212 to change, thus changji gthe current output of thetubes 214 and 216 andgthevoltagebias on the control grids oftubes 121 4 and 216. Withsufilcient light intensity on the photocell,tube 216 nolongerconducts current and tube 214 conducts current of less value than that required toretain relay coil I28 energized. While specific circuit constants have been used in connection with the description of the circuits of the present invention and their operation it will be understood by those skilled in the art that they are illustrative and that the circuits are capable of operation at other values than those recited.

With the light responsive circuits such as described above wherein'thelightresponsive relay controlling the headlamp filament circuit is in turn controlled byan amplifiercomprising two amplifiertubes in parallel, the energizing and deenergizing of theheadlamp filamentsis accomplished at substantially diiferent intensities of illumination. 'This important feature makes the operation of an automatic dimmer device for vehicle headlighting systems feasible because of the lack of response of the device to other sources of lightcausing flickering due to the repeated energization and 'deenergization of the high and lowbeam headlamp filaments.

What we claim as new and desire to obtain by Letters Patent of-the'United States is:

1. In alight-sensitive apparatus for controlling the energization and deenergization of an electromagnetic circuit controlling device, a source of power, alight-sensitive cell connected to said source and power amplifying means comprising aipair of amplifying tubes connected in parallelbetween said cell and said circuit controlling'olevice biased to-operate at different control voltages, and'cu-rrentlimiting means in series :withcneof the-amplifier tubes for selectively controlling th energization and deenergization of said circuitcontrolling device'at substantially different intensities of illumination of said cell.

In alight-sensitiveapparatus for control- .ling theenergization and deener'gization of an electromagnetic circuit controlling device, a source ofpower -alight-sensitive cell connected to said source, a primary amplifier connected to said cell, and a secondaryamplifier connected between said primary amplifier and said circuit controlling device for controlling the energization and deenergization of said circuit control- I ling device at substantially differentintensities tube connected to said cell and a pair of power amplifying tubes connected in parallel electrical relationship between said first mentioned tube and th circuit controlling device biased to operate at different voltages and current limiting means in series with one of the pair of amplifying tubes for selectively controlling the energization and deenergization thereof at substantially different intensities of illumination of said cell.

4. In a lighting system having a lamp with beam changing means and a source of power connectable thereto, a light-responsive device for controlling said means including a light-sensitive cell connected to said source, magnetic relay switching means for controlling said beam changing means and primary and secondary amplifying means connected between said cell and said relay means for selectively controlling the energization and deenergization of the relay means at substantially different intensity levels of illumination of said cell, said secondary amplifying means comprising a pair of amplifier tubes biased to operate at different control voltages and electrically connected in parallel to said means, and current limiting means in series with one of the tubes.

5. In a headlight system having high and low beam filaments, a source of power connectable thereto and manual switching means connected between the source and said filaments, light responsive means connected to said source for automatically controlling the energization of said filaments including a light-sensitive cell, magnetic relay switching means for selectively connecting said source to said filaments and an amplifying circuit comprising a pair of amplifying tubes electrically connected in parallel between said cell and said relay means biased to operate at different control voltages and current limiting means in series with one of the tubes for selectively controlling the energization and deenergization of the relay means at substantially diiferent intensities of illumination of said cell.

6. In a headlight system having high and low beam filaments, a source of power connectable thereto and manual switching means connected between the source and said filaments, light responsive means connected to said source for automatically controlling the energization of said filaments including a light responsive cell, an amplifying tube having its control grid connected to the output of said cell, magnetic relay switching means for selectively connecting said source to said filaments, a pair of amplifying tubes having their output connected in parallel relationship to said relay, circuits connecting the output of said first mentioned tube to the control grids of said last-mentioned tubes, means to bias said grids at different voltages, and current limitingmeans connected in series with one of the pair of tubes.

'7. In an amplifying system responsive to different intensities of illumination on a light-sensitive cell to control the energization and deenergization of an electromagnetic circuit controlling relay, a first amplifier tube and a second amplifier tube, said tubes having their plate circuits connected in parallel to the coil of said relay to provide current for the energization of said coil, a power source for said system, current limiting means connected between the first amplifier tube and relay and means interconnecting said cell and the control elements of said tubes for controlling current fiow in both tubes in response to different intensities of illumination on said cell to cause both tubes to conduct current to close the relay at a low intensity of illumination and cut off current flow in one tube While simultaneously reducing the current flow in the remaining tube to hold and subsequently open said relay with correspondingly increasing intensities of illumination.

8. In an amplifying system responsive to different intensities of illumination on a light-sensitive cell to control the energization and deenergization of an electromagnetic circuit controlling relay, a first amplifier tube and a second amplifier tube, said tubes having their plate circuits connected in parallel to the coil of said relay to provide current for the energization of said coil, current limiting means in the plate circuit of one tube, a power source for said system and means connected to said cell and to the control grids of said tubes for supplying substantially different variable biasing voltages to said grids in response to variations in light intensity on said cell to cause both tubes to conduct current to clos the relay at a low intensity of illumination and cut off current flow in one tube while simultaneously reducing the current flow in the remaining tube to hold and subsequently open said relay with correspondingly increasing intensities of illumination.

9. In an amplifying system responsive to different intensities of illumination on a light-sensitive cell to control the energization and deenergization of an electromagnetic circuit controlling relay, a source of power, a first amplifying circuit comprising a pair of amplifying tubes having their plate circuits connected in parallel with said relay coil to provide current for the energization of said coil, current limiting means in the plate circuit of one tube and a second amplifying circuit interconnecting said cell and the control elements of the amplifying tubes in said first amplifying circuit comprising an amplifying tube and means responsive to the current flow in said tube to control current flow in the tubes of said first amplifying circuit to cause both tubes of said circuit to conduct current to close said relay at a low intensity of illumination and cut off current flow in one tube while simultaneously reducing the current flow in the remaining tube to hold and subsequently open said relay with correspondingly increasing intensities of i1- lumination.

10. In an amplifying system responsive to different intensities of illumination on a light-sensitive cell to control the energization and deenergization of an electromagnetic circuit controlling relay, a source of power, a first amplifying circuit comprising a pair of amplifying tubes having their plate circuits connected in parallel with'said relay coil to provide current for the energization of said coil, current limiting means in the plate circuit of one tube, a second amplifytubesandthe input elements of the tubes of said first amplifying circuit to cause both tubes of said first amplifyingcircuit :to conduct current to closethe relay at a lowintensity of illumination and out oif current flow inone tube .while simultaneously reducing the current flow in the remaining tube to hold and subsequently open said relay with correspondingly increasing inten sities of illumination.

11. In an amplifying system responsive to different intensities of illumination on a light-sew sitive cell to control the energization and deenergization of an electromagnetic circuit controlling relay, a source of power, a first amplifying circuit comprising a pair of amplifying tubes connected in parallel with said relay coil to provide current for the energization thereof, current limiting means in the plate circuit of one tube, a second amplifying circuit interconnecting the cell and the control elements of the amplifying tubes in said first amplifying circuit comprising an amplifying tube and means responsive to ourrent fiow in said tube to control fiow in the tubes of said first amplifying circuit to cause both tubes to conduct current to close said relay at a low intensity of illumination and cut oil current flow in one tube while simultaneously reducing the current flow in the remaining tube to hold and subsequently open said relay with correspondingly increasing intensities of illumination, said means including a diode interconnectin the control elements of one tube of said first amplifying circuit and the plate circuit of the amplifying tube of said second amplifying circuit.

12. In a system for automatically dimming multiple filament headlamps, a regulated source of power, switching means for alternately ener giz-ing different filaments of the headlamps, light sensitive means connected to said source, amplifier means connected to said light sensitive means and relay means connected to the amplifier output and operating said switching means, said amplifier means including a pair of electronic tubes in parallel relation, biased to conduct at different input voltages and a limiting resistance in series with one of said electronic tubes to reduce the output for that tube so that relay energization and deenergization are accomplished at different levels.

13. A photoelectric relay circuit for automatic dimming of multiple filament headlights, comprising a photoelectric pickup device, a voltage regulated power supply, a voltage amplifier tube connected to the regulated power supply, and having the cathode of the pickup device connected to the control grid of the voltage amplifier tube, a current amplifier tube having the control grid thereof connected to the plate of the voltage amplifier tube, a relay in the plat circuit of the current amplifier tube, said relay being normally electrically energized in the absence of light and tie-energized upon the application of light to the phototube, and a switch operated by the relay to change the power source from the headlight high beam filament to the headlight low beam filament when it is de-energized by light falling on the pickup device, and upon the removal of the light to change the power source back to high beam filament.

14 14. In a control system for multiple filament headlamps of a motor vehiclewhichprovide high beam or long range road patterns and low'beam or short range road patternsahead of the vehicle, a source of electrical power, switching means interconnecting the source of power alternately withthe highbeam or low beam filaments, relay means for operating the switching means, a light sensitive device connected to the source of power and electronic amplifier means connected between the sensitive device and the relay to control the operationotthe latter bythenamount of light falling on the light sensitive device, said amplifier means including electronic meansdifferently biased to control current'fiow through the relay to cause energization and deenergization of the relay at different predetermined illumination levels falling on the light sensitive device.

15. In a control system for multiple filament headlamps of a motor vehicle which provide high beam or long range road patterns and low beam or short range road patterns ahead of the vehicle, a source of electrical power, switching means interconnecting the source of power alternately with the high beam or low beam filaments, relay means for operating the switching means, a light sensitive device connected to the source of power and electronic amplifier means connected be--- tween the sensitive device and the relay to control the operation of the latter by the amount of light falling on the light sensitive device, said amplifier means including electronic means, and means to control the current flow through the electronic means so that the relay will be energized and deenergized at substantially different outputs of the light sensitive means.

16. In a system for automatically dimming multiple filament headlamps, a source of power, switching means for alternately energizing different filaments of the headlamps, light sensitive means connected to said source, amplifier means connected to said light sensitive means, and relay means connected to the amplifier output and to the switching means, said amplifier means including electronic means biased to conduct at different applied voltages determined entirely by levels of light intensity falling on the sensitive means.

17. In a system for automatically dimming multiple filament headlamps, a source of power. switching means for alternately energizing different filaments of the headlamps, light sensitive means connected to said source, amplifier means connected to said light sensitive means, and relay means connected to the amplifier output and to the switching means, said amplifier means including parallel conductive paths limited to conduct different amounts of current and conductive biased means in each path differently adjusted to conduct at differing outputs of the light sensitive means determined by differing levels of illumination.

18. In an amplifying system responsive to different intensities of illumination on a light sensitive cell to control energization and deenergization of an electromagnetic circuit controlling relay, a source of power, a first amplifying circuit comprising a pair of amplifying tubes having their plate circuits connected in parallel with said relay coil to provide current for the energization of said coil, a second amplifying circuit connected between the input elements of the tubes of the first amplifying circuit and said sensitive cell and biased rectifying means included in the connection between the second 15 amplifying means and the input elements of, one of the tubes of the first amplifying means to cause both tubes of said first amplifying circuit to conduct current to close the relay at a 10W intensity of illumination falling on said cell and 5 cut offcurrent flow in one tube While simultaneously reducing the current flow in the remainingtube to hold and subsequently open said relay with correspondingly increasing intensities. 10

References Cited in the file of this patent UNITED STATES PATENTS I Number Name Date 2,150,900 Alley Mar. 21, 1939 15 Number Number Name Date Berg, Jr. Oct. 29, 1940 Gillespie May 6, 1941 Cockrell Nov. 24, 1942 Willis, Jr. July 31, 1945 Friedman Nov. 25, 1947 Gieseke Dec. 30, 1947 Moore et a1 Jan. 3, 1950 FOREIGN PATENTS Country Date France Nov. 16, 1933 

